Varifocals are a special type of corrective lens that is used in eyeglasses to correct presbyopia and other vision disorders of accommodation. varifocals (Gleitsichtbrille) are also known as progressive or spectacle lenses, progressive addition lenses, progressive power lenses, multifocal lenses, or graduated prescription lenses.
Varifocals can be distinguished from other types of corrective lenses by their gradient approach to correction, which utilises different lens power ratios at different areas on the lens. In the majority of cases, varifocals will have their minimum addition power at the top of the lens for distance perception and their maximum addition power at the bottom of the lens for close and reading perception.

The Design and Construction of Varifocals

While all varifocals lenses use this method of increasing lens power throughout the lens, the actual length of the progressive gradient will depend on the refractive index, which is different for everyone. Most people who require varifocals use an index of between 0.75 and 3.0 dioptres, with additional values sometimes prescribed for extreme cases of presbyopia and related conditions. Varifocals are so useful because of the different ways that they can be worn, with users able to tilt their head and their glasses to sight through the appropriate part of the lens. Because different gradients are associated with different areas of the vertical progression, people are easily able to correct their vision in a wide range of situations.

However, there are some disadvantages associated with the wearing of varifocal lenses, including some distortion and the loss of peripheral vision. People relate to these disadvantages in different ways, with some people unable to wear varifocals and others having no problem with them whatsoever. The cost of varifocals can also be prohibitive for some people, as they are almost always more expensive than bifocals and single reading glasses. However, varifocal lenses are used by a large proportion of people who need corrective glasses, due to their flexible nature and their ease of use in a variety of situations.